Preference control mechanisms for use in adjusting the force required to tilt back a chair or tilt or rotate other chair components are often included in various chairs. For example, preference control mechanisms are disclosed in U.S. Pat. Nos. 4,865,384, 4,889,384, 5,106,157, 5,192,114, 5,370,445, 5,385,388, 5,388,889, 5,909,924, 6,742,843 and 6,932,430.
Chair tilt controls often utilize a spring that acts on a backrest to bias the backrest to an upright position. Some types of preference control mechanisms are configured so that a user may select a desired preference setting for the force provided by this spring. Such preference controls can permit heavy weighted users to adjust the force required to tilt a backrest to a reclined position so that the heavy user may experience the same recline ride as a lighter user. Such preference controls may also permit users to select the biasing force that provides a preferred recline ride. For instance, a lighter user may prefer a first setting that permits a relatively weak biasing force to act on the backrest. The preference control may be configured to permit a heavier user to adjust the biasing force exerted by the spring of the chair tilt mechanism so that a greater force acts on the back to bias the back to an upright position so recline of the backrest requires more force to be exerted.
Other types of preference control mechanisms are operatively connected to the back of a chair or to a tilt mechanism of the chair to adjust the extent to which the back of the chair may be reclined. Such mechanisms may set a limit that defines a most tilted position or may lock the tilted position of a backrest.
Due to the design of some preference control mechanisms, damage to the preference control mechanism or other portion of a chair may be caused by a user attempting to readjust the preference setting while the chair back is reclined. Indeed, some preference control designs are configured to only permit such adjustment when a chair component is in an upright position or a non-tilted position to prevent such damage.
Some preference control mechanisms are configured to act directly on a tilt spring to adjust the force exerted by that spring to bias the back of the chair to an upright position. For chairs configured to have their seat and backs synchronously tilt, one or more tilt springs may be configured to bias the back and seat of the chair to their respective upright positions. Typically, preference control mechanisms that adjust the force provided by the tilt springs include one or more members that engage or act on the one or more tilt springs. In some cases, the one or more preference control members may break when their positions are adjusted while the back or seat of a chair is in a reclined position due to the tension of the one or more tilt springs.
A device is needed to prevent damage from occurring during preference control adjustment of the biasing force exerted by a chair tilt mechanism. Preferably, the device is configured to permit adjustment even when the back or seat of a chair is in a reclined position without causing damage to the preference control mechanism or the chair.